The present invention relates to an electric power supply system for a vehicle, and particularly to an electric power supply system for use in a vehicle such as an automobile and the like, in which an electric power is supplied to electrical loads from a power supply source such as a battery for an automobile.
In a conventional electric power supply for a vehicle, for example, in an electrical power supply system for an automobile, in order to supply power from a battery to its electrical loads such as lamps, motors and the like, a plurality of power lines are laid out for connecting between respective electrical loads and the battery. For a recent automobile, which has an increased number of electrical loads compared to the conventional automobile, the number of power lines has increased significantly. Further, because it is necessary to provide power lines not only for connection between respective electrical loads and the battery but also for connection between switches that control the respective electrical loads and the battery, a total distance of extension of the power lines has increased substantially. Any such increases in the number of power supplies and the total distance of extension of power lines, which leads to an increase in weight of the vehicle body, will deteriorate fuel mileage.
Therefore, for example, as described in the brochure of International Publication WO 96/26570 (1996), it is proposed that by connecting a plurality of relay circuits (control modules) to a power line which is laid out in a loop, then a plurality of electrical loads are connected respectively to each of these relay circuits through which to supply power thereto.
However, the prior art disclosed in the brochure of International Publication WO 96/26570 (1996) is associated with one problem that because every control modules are connected to a single loop power line, if a fault occurs in one of the control modules, the other control modules may be affected, and in a worst case, it becomes difficult to control the engine itself, which is an essential function for the automobile.
Further, the prior art disclosed in the brochure of the International Publication WO 96/26570 (1996) is associated with a second problem as will be described below. Although when the power line is short-circuited, its electrical loads are isolated from the power line by operating its switching devices, no countermeasure, however, is taken for a case where an over-current flows through an electrical load due to failure in the electrical load itself or the like. In order to prevent the occurrence of over-current, a fuse may be used. However, in order to improve easiness of fuse exchange, it has been preferred to place a plurality of fuses in one concentrated area. In order to place the plurality of fuses in one concentrated area, it becomes necessary to provide for additional power lines to connect between the plurality of fuses that are placed in one concentrated area and their associated electrical loads, consequently failing to reduce the length of the power lines.
The prior art technologies similar to the above are disclosed in the following documents. JPA Laid-Open Nos. 9-275632, 10-4632, 10-20970, U.S. Pat. Nos. 4,652,853 and 4,739,183.
A first object of the invention is to provide for an electric power supply apparatus for a vehicle, which minimizes proliferation of adverse effect on the other control modules than that is directly involved.
A second object of the invention is to provide for an electric power supply apparatus for the vehicle, which can reduce a total length of its power lines.
(1) The above objects of the invention can be accomplished by provision of an electric power supply system which is comprised of: an electric power source, a plurality of control modules for a plurality of accessory systems connected to the electric power source via a power line; and a power control module for controlling a drive source of the vehicle, which is connected to the electric power source via another power line that is different from the above-mentioned power line.
According to this arrangement described above, because of the provision of the another power line for supplying power of PCM for controlling the engine itself, which is independent from the power line PL for the accessory systems, PCM 20 for controlling the engine is ensured to function normally even if a failure of the control modules for the accessory systems occurs.
(2) The above objects of the invention can be accomplished by provision of an arrangement which is comprised of: an electric power source; a plurality of control modules for a plurality of accessory systems, which are connected to the electric power source via electric power line; and an air-conditioner, which is connected to the electric power source via another power line that is different from the above-mentioned power line.
According to this arrangement of the invention, because of the provision of a dedicated power line for the air-conditioner that consumes a large electric current independent from the power line PL for the accessory systems, normal operation of the automobile is ensured even if the air-conditioner fails.
(3) The above-mentioned objects of the invention can be accomplished by provision of an arrangement which is comprised of: an electric power source; a plurality of control modules for a plurality of accessory systems connected to the electric power source via power lines; and an information device that is connected via another power line which is different from the above-mentioned power lines.
According to this arrangement of the invention, because of the provision of a dedicated power line for the auxiliary information device that assists the operation of the automobile independent from the power lines PL for the accessory systems, the normal operation of the automobile is ensured even if the information device fails.
(4) The above-mentioned objects of the invention can be accomplished by provision of an arrangement which is comprised of: an electric power source; a plurality of control modules for a plurality of accessory systems connected to the electric power source via power lines; a plurality of input means for inputting an input signal to these control modules; a plurality of electrical loads; a plurality of switch devices each connected between the electric power line and the plurality of electrical loads, and having a protection function; and a signal line for transmitting a signal between the plurality of the control modules for the plurality of the accessory systems, wherein by using data processing means provided at least in one of the plurality of the control modules for the plurality of accessory systems, the switch device is controlled in response to an input signal from the input means so as to supply power from the power source to the electrical load via the power line.
According to this arrangement as described above, because the electrical load is supplied with power from supply line PL via its switching device that is controlled by its control module, it becomes possible to reduce the number of power lines, and further, by using as its switching device a MOS FET provided with a protective function, which can prevent for a total length of the power line from increasing due to a necessity of its lengthy layout, it becomes possible to minimize the power lines in the electric power supply system for the vehicle.
(5) The first and the second objects of the invention can be accomplished by provision of an arrangement according to the invention that is comprised of: a power source; a plurality of control modules for a plurality of accessory systems connected to this power source via a power line; a switching device that is connected between the power line and an electrical load, has a protective function, and is controlled in response to a signal from the control module so as to supply power to the electrical load from the power source via the power line; and a power control module that is connected to the power source via another power line different from the above-mentioned power line for controlling the drive source of the vehicle.
According to this arrangement of the invention, because of the provision of an independent power line for supplying power to PCM for controlling the engine itself, which is different from the power line PL for the accessory systems, it becomes possible for PCM 20 which executes the engine control to be ensured to operate normally even if there occurs a failure in the other control modules for the accessory systems. Further, because the electrical load is supplied with power from the power line PL via the switching device that is controlled by the control module associated therewith, it becomes possible to reduce the number of power lines. Still further, because the MOS FET provided with the protective function is used as its switching device, which can prevent for the total length of the power lines from increasing due to a lengthy extension of layout of the power lines, the length of the power lines in the electric power supply system for the vehicle can be minimized.